Update docker doc

README.md

@@ -80,11 +80,11 @@ java -jar target/dil-demo.jar
 
 ## Docker builds
 
-To build and run a docker image, do
+To build and run a docker image locally, with the configuration environment vars in a `.env` file, and keys and certificates in `./credentials`, do
 
 ```sh
 docker build . -t my-image
-docker run --env-file=.env my-image
+docker run --env-file=.env --mount="type=bind,source=${PWD}/credentials,destination=/credentials" -p8080:8080 my-image
 ```
 
 The above assumes your environment variables are specified in `.env`